A pre-distortion apparatus and method for recovering nonlinear distortion of a high power amplifier. In a digital servo which executes an output equation ydkCxkDudk and state equation xk1AxkBudk. The seat structure, handlebar structure, drive train and support platforms are all able to be readily attached to the primary frame structure to provide an exercise bicycle that is sturdy, easy to manufacture, and light enough to easily move when necessary.